1. Field of the Invention
This invention relates to a method for manufacturing a regenerated catalyst using a spent catalyst that has been used in the hydrorefining of a petroleum distillate and for reusing the regenerated catalyst. It also relates to a method with which the vanadium and other metals contained in a heavy oil are recovered by hydrorefining.
2. Description of the Related Art
A hydrorefining catalyst is generally manufactured by supporting molybdenum and other such hydrogenation active metal components on a porous carrier such as alumina. Hydrorefining reduces the amount of sulfur, nitrogen, metals such as vanadium, and so forth in a heavy oil. Hydrorefining involves bringing a hydrocarbon oil into contact with hydrogen in the presence of a catalyst, cracking the sulfur compounds and other such hetero compounds, and separating these out as hydrogen sulfide, ammonia, and the like.
When hydrorefining is continued for an extended period of time, coke and metals are deposited into the catalyst pores and lower the catalytic activity. This degradation is particularly pronounced when the hydrocarbon oil is a heavy oil. Accordingly, a used desulfurization catalyst whose catalytic activity has decreased is removed as a spent catalyst and replaced with a new catalyst. The removed spent catalyst can be disposed of as waste by burying it after any oils have been removed and, in some cases, after metals such as vanadium and molybdenum have been recovered. The remaining alumina from which the metals have been recovered is also sometimes utilized in applications other than as a catalyst, such as a raw material for aluminum sulfate.
A spent catalyst in which very little vanadium or other metals have been deposited is also sometimes reused as a catalyst after the removal of coke. It may also be reused after the metals have been taken out by dissolution.
Still, the activity of a catalyst obtained by a conventional recycling method is not as high as that of a new catalyst. Also, the mechanical strength is diminished by treatments such as calcination performed in order to remove the coke. This decrease in mechanical strength is a problem in that the catalyst breaks up into a powder when repacked into the reactor. Consequently, the reuse of such catalysts has been limited.
Hydrorefining can also be thought of as a treatment by which vanadium and other metals are recovered from a petroleum distillate by means of a catalyst, in which case the metal content in the catalyst that has been used in hydrorefining (spent catalyst) must be raised in order to recover the metals more efficiently. Hydrorefining catalysts have not been studied from this standpoint up to now.
The present invention was achieved in an effort to solve the problems encountered with the above conventional art, and a first object thereof is to provide a method for manufacturing a hydrorefining catalyst that exhibits high activity in a specific reaction by using a catalyst that has been used in hydrorefining. A second object of the present invention is to provide a method for recovering metals at a high efficiency through hydrorefining.